The present invention relates to a technique for detecting or identifying, from a sound signal, a repetition of a plurality of portions that are similar to each other in musical character.
Heretofore, there have been proposed various techniques for identifying, from a music piece, a portion where a musical character of performance tones satisfies a predetermined condition. Japanese Patent Application Laid-open Publication No. 2004-233965, for example, discloses a technique for identifying a refrain (or chorus) portion of a music piece by appropriately putting together a plurality of portions of a sound signal, obtained by recording performance tones of the music piece, which are similar to each other in musical character.
The technique disclosed in the No. 2004-233965 publication can identify with a high accuracy a refrain portion of a music piece if the music piece is simple and clear in musical construction (e.g., pop or rock music piece having clear introductory and refrain portions) and the refrain portion continues for a relatively long time (i.e., has relatively long duration). However, with the technique disclosed in the No. 2004-233965 publication which is only intended to identify a refrain portion of a music piece, it is difficult to identify with a high accuracy a particular portion of a music piece where one or more portions each having a short time length (i.e., short-time portions) are repeated successively, e.g. a piece of electronic music where performance tones of a bass or rhythm guitar are repeated in one or more short-time portions each having a time length of about one or two measures.